1. Field of the Invention
The present invention relates to a nitride semiconductor substrate, a semiconductor device and methods for manufacturing the nitride semiconductor substrate and the semiconductor device, and more particularly to a nitride semiconductor substrate having a main surface serving as a semipolar plane, a semiconductor device, and methods for manufacturing the nitride semiconductor substrate and the semiconductor device.
2. Description of the Background Art
A nitride semiconductor substrate such as a GaN substrate having an energy band gap of 3.4 eV and a high thermal conductivity has been attracting attention as material for a semiconductor device such as a power electronic device and an optical device of a short wavelength. In order to prevent chipping, cracking and the like of the substrate, it is proposed to provide a chamfered portion at the edge of the outer periphery in the GaN substrate which is an example of the above-described nitride semiconductor substrate (for example, see Japanese Patent Laying-Open No. 2004-319951).
However, Japanese Patent Laying-Open No. 2004-319951 as described above discloses a substrate having a main surface corresponding to the c-plane, but fails to disclose a nitride semiconductor substrate having a main surface serving as a semipolar plane (main surface inclined from the c-plane). Furthermore, it is not known what type of chamfered portion is formed at the edge of the outer periphery in the nitride semiconductor substrate conventionally having such a semipolar plane as a main surface in order to effectively reduce cracking and chipping of the nitride semiconductor substrate.